There can be no doubt that when you accepted a position in President Trump's Cabinet, you did so out of a sense of duty. Your views on border security and concerns about immigration and social cohesion seem genuinely felt. I believed you when you said that running the Department of Homeland Security, if only for six months, was "one of the great honors" of your life — a life that already had many great honors and achievements to its credit.

I wonder, though. When did you begin to feel a twinge of doubt? Was it when, reportedly "stunned," you watched the president sign the "travel ban" executive order that you believed was still under discussion? Or was it sooner than that? Perhaps even during the transition period in Bedminster, New Jersey? Whatever it was that drove you to the brink — the end-running around your authority by the two-headed monster known as "Javanka," or, needless to say, Trump's own mercurial fits and rages and stupidity — nearly every decent American could sympathize with you when you joked that your tenure as White House chief of staff was tantamount to a punishment from God.

How about this: Tell us the truth. The whole, ugly, unmitigated truth. Tell the American public what it was like working for a man like Donald Trump. Give us your version of the daily presidential potty-training that former Secretary of State Rex Tillerson recently described during a fundraiser in Houston:

When the president would say, "Here's what I want to do, and here's how I want to do it," and I'd have to say to him, "Well, Mr. President, I understand what you want to do, but you can't do it that way. It violates the law, it violates the treaty, you know." He got really frustrated … I think he grew tired of me being the guy every day who told him he can't do that and let's talk about what he can do. [Tillerson]

Hold that thought. Because I'm sure that Trump's crude response to Tillerson ("dumb as a rock," "lazy as hell") is crossing your mind. Maybe you're thinking, wouldn't it just be easier to leave on relatively decent terms?I'm still a decorated general officer. I tried my best to wade through the "cesspool of domestic politics." The president still refers to me as a "great guy." Why not leave it that?

The thing is, your reputation is already, alas, besmirched. You ultimately did not bring a chaotic White House under control. You did not bring an inexperienced, reckless president to heel. And, worst of all, you will forever be associated with an unconscionable migrant family separation policy that history will remember as cruel and pointless and ineffective on its own terms.

Maybe you'd prefer a long period of reflection. Maybe you're planning on writing a memoir, with your tumultuous tenure in the Trump administration merely a footnote to a distinguished career of military service and valor. But the public needs to know the truth now. The "adults in the room," as men like you and Defense Secretary James Mattis are called in the Washington press corps, are always mentioned in the context of having prevented Trump from his worst impulses. The public deserves to know exactly where those impulses would have led us.

Sometime within the next year, it's going to become apparent to all but the most incorrigible #MAGA dead-enders that Trump is going to be remembered as one of the most despised figures in the history of American politics — a president of unfathomable corruptibility and plain incompetence.

General Kelly, you are now about to disembark from this particular journey. It's no longer in your job description to maintain the fiction that Trump is fit for high office. You don't need to protect the man anymore. And if you truly want to protect the country that you would have died for — that your son died for — it's incumbent on you to spill the beans.